Spatial Density and Distribution of Tumor-Associated Macrophages Predict Survival in Non–Small Cell Lung Carcinoma

Abstract

The respective antitumoral and protumoral roles of M1 and M2 tumor-associated macrophages (TAM) typify the complexity of macrophage function in cancer. In lung cancer, density and topology of distinct TAM phenotypes at the tumor center (TC) versus the invasive margin (IM) are largely unknown. Here, we investigated TAM subtype density and distribution between TC and IM in human lung cancer and TAM associations with overall survival. Macrophages isolated from adjacent nontumor tissue (NM), the TC (TC-TAM), and the IM (IM-TAM) were analyzed with RNA-sequencing (RNA-seq). Lung tumor tissue microarrays from 104 patient samples were constructed. M1 and M2 TAMs were identified using multiplex immunofluorescence staining and a tumor cell-TAM proximity analysis was performed. RNA-seq identified marked differences among NM, TC-TAM, and IM-TAM. On the basis of a panel of five selected markers (CD68, IL12, CCR7, CD163, and ALOX15), M2 predominance over M1 and M2 proximity to tumor cells was observed, especially at IM. Tumor cell proximity to TAM was linked with tumor cell survival and hypoxia was associated with accumulation of M2 TAM. Notably, lower density of M1 TC-TAM and higher proximity of tumor cells to M2 IM-TAM or lower proximity to M1 IM-TAM were linked with poor survival. In addition, three novel molecules (UBXN4, MFSD12, and ACTR6) from RNA-seq served as potential prognostic markers for lung cancer, and M2 predominance and juxtaposition of M2 TAM near tumor cells were associated with poor survival. Together, our results reveal the marked heterogeneity of TAM populations in different tumor regions, with M2 TAM predominance, particularly at IM. Significance: This study underlines the significance of the density, spatial distribution, and gene expression of TAM phenotypes as prognostic factors for overall survival in lung cancer.

Meta-Analysis of Microdissected Breast Tumors Reveals Genes Regulated in the Stroma but Hidden in Bulk Analysis

“…Interestingly, we find genes with opposite regulation in tumor epithelium and tumor stroma, which compartment-specific regulation would have not been found with bulk data: genes up-regulated in tumor stroma and down-regulated in tumor epithelium are enriched for cytokine secretion and Toll-like receptor 2 signaling, suggesting that the microenvironment produces different sets of cytokines than the tumor itself, possibly reflecting different chemoattraction and hence different immune cell proportions depending on tumor proximity. Indeed, immune cells' distribution has been found to be of clinical relevance in cancer [121][122][123].…”

Is the C-C Motif Ligand 2–C-C Chemokine Receptor 2 Axis a Promising Target for Cancer Therapy and Diagnosis?

“…An increase in the number of TAMs generally shortens survival and increases the grade and stage of cancer. Specifically, they have been reported in gastric cancer, breast cancer, prostate cancer, classical Hodgkin's lymphoma, kidney cancer, nasopharyngeal cancer, and glioma [44][45][46][47][48][49][50][51][52]. CCL2-induced chemokine cascade promotes breast cancer metastasis by enhancing retention of TAMs [53].…”

Non-genetic Heterogeneity of Macrophages in Diseases—A Medical Perspective

“…As it was shown that AMs were not significant contributors of TAM population in lung cancer (Loyher et al, 2018), we can hypothesize that TAMs actually originate exclusively from adult monocytes, with a varying time of residency within the tissue. In patients suffering from non-small cell lung carcinoma (NSCLC), another recent study highlighted a spatial heterogeneity between TAMs located in the tumor core and TAMs located at invasive margin (Zheng et al, 2020). Indeed, pro-tumoral TAMs were marked especially at the tumor-invasive margin.…”

“…Moreover, pro-tumoral TAMs were in closer contact to tumor cells as compared to the antitumoral ones. Finally, at the invasive margin, higher proximity of tumor cells to pro-tumoral TAMs and lower proximity to antitumoral TAMs were associated with poor survival (Zheng et al, 2020). Finally, another recent study of human and mouse NSCLC identified a new population of mature dendritic cells enriched in immuno-regulatory molecules (mregDCs) that limit antitumor immunity (Maier et al, 2020).…”